Display screen or portion thereof with a transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with atransitional graphical user interface, showing our new design anddepicting a first image of the transitional graphical user interface.

FIG. 2 is a front view depicting a second image of the transitionalgraphical user interface.

FIG. 3 is a front view depicting a third image of the transitionalgraphical user interface.

FIG. 4 is a front view depicting a fourth image of the transitionalgraphical user interface.

FIG. 5 is a front view depicting a fifth image of the transitionalgraphical user interface.

FIG. 6 is a front view depicting a sixth image of the transitionalgraphical user interface.

FIG. 7 is a front view depicting a seventh image of the transitionalgraphical user interface.

FIG. 8 is a front view depicting an eighth image of the transitionalgraphical user interface; and,

FIG. 9 is a front view depicting a ninth image of the transitionalgraphical user interface.

The appearance of the transitional graphical user interface sequentiallytransitions between the images shown in FIGS. 1-9. The process or periodin which one image transitions to another image forms no part of theclaimed design.

The broken lines illustrate environmental subject matter, and form nopart of the claimed design.

CLAIM The ornamental design for a display screen or portion thereof witha transitional graphical user interface, as shown and described.